2 odes of operation
Deco e PRM4 evice can operate in one of the two mo es of operation.
When powere , the evice will automatically enter the efault, data transfer mo e.
When the evice is in the data transfer mo e, it will listen an receive all the packets
inten e for it, whereas the transmitter will turn-on only occasionally to sen the ata
acquire from the wire connection.
The mo e an parameters of operation are set through the use of AT comman s using
the command mo e of operation. The transfer into the command mo e an the set of
supporte AT comman s is escribe in chapter 4.
The PRM 4 evice supports an a ressing scheme. All mo ems inten e for ata
exchange in a ra io network must be set to the same frequency an must have the
same network address (NA). The NA can be set to any value from the 0 – 65535
range. Each evice has its source address (SA) use to i entify the evice insi e a
network. The SA can take values between 0 an 255 inclusive. Note that the SA must
be set uniquely insi e a network. If a point-to-multipoint connection is require (e.g.
for master-slave protocols use with SCADA software or PLC evices) the
destination address (DA) masking is use . This way it is possible to mask a number
of bits when comparing the DA an SA an , consequently, the packet with one
estination a ress can be sent to multiple evices having the unmaske parts of their
SA match the unmaske parts of DA.
For example, if assume that the ra io frequency an the NA are the same for all the
evices in the following figure, the evice with the SA equal to 100 will sen its
packets to the remaining three evices, whereas the evices with the SA 1,2 an 3 will
sen ata only to the SA 100 evice. This is because the Address Masks (AM) on
evices with SA 1,2 an 3 have been set to 252 (binary 11111100) so that they match
the higher (unmaske ) six bits of the DA (binary 000000).
Ra io mo em PRM4 868MHz /User's manual V1.6 / 24.05.2011 5
